Reciprocating drilling tool



June so, 1970 w, w, CRUMBO 3,517,759

RECIPROCATING DRILLING TOOL Filed May 10, 1968 INVENTOR WOODROW W! CRUMBO BY 77% g 5 ATTORNEYS United States Patent U.. Cl. 175-298 3 Claims ABSTRACT OF THE DISCLOSURE The invention consists of a rotary-type drilling tool carrying a plurality of reciprocating and self-rotating drill bits.

The tool includes a hollow housing in which is seated a cam imparting a reciprocating drilling action to the push rods of cylindrical drill bits, the latter being arranged peripherally around a central drill pipe. Each of said drill bits is free to rotate on the axis of its push rod, and a portion of its periphery extends beyond the diameter of the housing into contact with the sidewalls of the borehole. Consequently rotation of the tool causes reciprocatory drilling action by the bits while sidewall contact by the bits causes constant changes in the position of the teeth carried by each drill bit with respect to the earth formation being drilled.

BACKGROUND OF THE INVENTION US. Pat. No. 3,384,190 dated May 21, 1968 shows a rotary-type drilling tool having a housing 11 carrying a central drilling member 14 and a disc-type cam 20* for rotation therewith. Disposed in the housing beneath the cam and motivated thereby are a plurality of wedgeshaped drill bits 30 radially disposed about the member '14. When bits 30 encounter a formation, their non-active rotational movement along with the housing is interrupted and a reciprocating drilling action is commenced due to cam 20.

SUMMARY OF THE INVENTION The present invention proceeds partly according to the above general plan, the principal difference and improvement being in the substitution for said wedge-shaped drill bits, of a plurality of cylindrically shaped bits mounted each on a drive rod and capable of separate rotation around the axis of each said rod. These cylindrical bits are arranged to protrude laterally externally of the housing diameter into contact with the side walls of the drill hole, and thus are rotated either by frictional contact with said side walls or by inertial counter-rotation to that of the rest of the tool, as will be further explained in detail.

The cylindrical bits being provided with teeth for drilling at the base of the drill hole, the above described rotational action of the bits presents the teeth of the bits in successively different positions with respect to the formation as their reciprocatory drilling motion proceeds, and thus greatly enhances the drilling action.

In the drawing:

FIG. 1 is an elevation of the bottom of the tool;

FIG. 2 is a vertical section taken on lines 2-2 of FIG. 1;

Patented June 30, 1970 FIG. 3 is a sectional detail of the cam member 20'.

The tool, generally indicated at 10, includes a housing 11 having a central threaded bore 12, for attachment to the end of a drill string (not shown). Housing 11 also has a hollow sleeve-like depending portion 13 in which the remaining parts are housed.

The central drilling member 14 is pipe-shaped for most of its length and at' its top is threadedly connected to the housing 11 for passage of drilling fluid pumped down the drill string and bore 12. The lower portion 15 of member 14 is of more solid construction to support a drag-type bit 16 having an offset fluid passage 17 (FIG. 1).

A disc type cam 20 is splined to the central member 14- and rotates therewith, cam 20 being capable of relatively vertical movement. A relief spring 22 is interposed between the top of cam 20 and the internal face of housing 11 to prevent cam 20 from overloadingthe mechanisms operated by it, about to be described. Cam 20 carries a depending flange 23 sinuously curved in such manner to provide relatively projecting portions 24 separated by relatively indented portions 25. These portions 24-25 are adjusted by their number and spacing to provide the camming action required for the selected number of drilling bits 30 next to be described.

In the example given in the drawing, there are peripherally arranged around and adjacent to the portion 15 of member 14 the four reciprocating drill bits 30. Each bit 30 has drill teeth 31 on the lower face facing the formation to be drilled.

Each bit is cylindrical (i.e. circular in cross-section) and each bit is rotatably mounted on a drive rod 35. Each drive rod 35 is rotatively and slidably mounted in a bore formed in the sleeve-like drive rod guide 36 which also has a central bore for central drill member 14. The upper tips of rods 35 are shaped with flanges 37 to contain the drive rod retracting springs 38, and are rounded or domeshaped at 40 for riding contact with the flange 23 of cam 20.

It will be further seen from the drawing that the drill bits 30 are so shaped and so mounted in guide 36 that a portion of the periphery of each bit 30 extends laterally beyond the circumference of housing 11.

OPERATION In a rotary drilling operation, a rotary clockwise motion will be imparted to the tool by the drill string. The tool, when encountering soft formations, will drill mainly by the use of the central drilling member 14. However, when sufiicient resistance is encountered, one or more of the drill bits will become engaged with the formation, and at this point the clockwise motion of the drill bits and their supporting members will become relatively checked or impeded compared to the rest of the tool.

The cam 20 will thus commence to operate against the drive rods 35 causing the drill bits 30 to reciprocate in a sequential fashion, increasing the drilling action. Concurrently, however, there still being some clockwise motion of the drill bits along with the tool, the sidewalls of the bits 30 will meet frictional resistance with the sidewalls of the borehole, and hence tend to revolve relatively in a counterclockwise direction. This same effect is also produced due to the force of inertia in the bits 30, these 3 t tending to rotate counterclockwise on their respective axes in reactionto the clockwise rotation of their common housing, guide 36.

What is claimed is:

1. In a drilling tool, in combination, a tool housing having means for attachment to a conventional string of drill pipe for use in a rotary earth boring operation in a drill hole; a depending hollow member centrally attached to said housing for rotational movement therewith; a cam member resiliently mountedon said hollow member for rotational movement therewith; a plurality of drill bits provided with drill teeth. on their earth-contact faces, said drill bits being mounted on push rods circumferentially disposed in said housing around said hollow member for reciprocatory drilling movement, and also for independent rotary movement on the axes of said push rods,'th'e push rods and bits being urged into reciprocatory drilling action by making contact with said cam member, said drill bits further being shaped and mounted in such position that a portion of each bit makes fric tional contact with the sidewall of the drill hole, the said frictional contact causing rotation of each drill bit on its own axis and consequent alteration of the position of the drill teeth carried thereby with respect to successive drilling strokes.

2. The invention according to claim 1, wherein said drill bits are cylindrically shaped, the curved sidewalls of said bits making frictional contact with the sidewall of said drill hole.

3. The invention according to claim 2, wherein said drill bits are mounted in such position that a portion of said curved sidewalls constantly extends beyond the periphery of said housing.

References Cited UNITED STATES PATENTS Thompson 17596 DAVID H; BROWN, Primary Examiner US. l. X.R. 175l0'6, 299 

